Damascus - Syria will not use chemical or other unconventional weapons except in the case of a foreign attack, foreign ministry spokesperson Jihad Makdissi said on Monday.
"Syria will not use any chemical or other unconventional weapons against its civilians, and will only use them in case of external aggression," Makdissi told a media conference in Damascus.
"Any stocks of chemical weapons that may exist, will never, ever be used against the Syrian people," he said, adding that in the event of foreign attack, "the generals will be deciding when and how we use them".
Fears have been rising that President Bashar al-Assad's regime might be prepared to use the country's arsenal of chemical weapons in the repression of a 16-month insurgency after reports his stocks were being moved around the country.
The statement came a day after the US said it would "hold accountable" any Syrian official involved in the release or use of the country's chemical weapons.
Neighbouring Jordan's King Abdullah II also said that in the event of a descent into all-out war, chemical weapons could fall into the hands of extremists, including certain rebel groups.
Meanwhile, the head of the Syrian Observatory for Human Rights watchdog told AFP on Monday that at least 23 people had been "summarily executed" by regime forces in two Damascus neighbourhoods on Sunday.
"Sixteen people, most of them younger than 30, were summarily executed by shooting on Sunday in Mazzeh," Observatory chief Rami Abdel Rahman said, referring to an upscale district in western Damascus.
Seven others were executed in a similar fashion in Barzeh in the city's north east, he said.
It was unclear whether the executions were of civilians or rebels fighters.
The heads of two of the victims had been crushed by vehicles, and one was shot through the eye, the Britain-based Abdel Rahman said.
Three of the dead were found with their hands tied, and the bodies of some had been pierced by bayonets, he added.
Overnight, Syrian state television reported an assault on Mazzeh, calling the operation "targeted and quick".
The broadcaster showed footage of troops firing as they entered part of the neighbourhood and featured an interview with one soldier.
"We came to the Mazzeh area at the request of citizens to fight the terrorists, who have been eliminated," he said.
The state broadcaster also reported that regime forces "chased the remnants of the terrorists in Barzeh".
The operation caused "heavy losses among them, including deaths and injuries. A number of the terrorists were arrested and dozens of them surrendered", the report said.